Scanning method and apparatus



Dec. 24, 1940. 5 1 CLQTHIER ETAL 2,226,508

SCANNING METHOD AND APPARATUS Filed March 20, 1939 4 Sheets-Sheet 1 I l O m @1 9 33 i H v J? 3% 9% INVENTORS Stewart 1.. Clothier & B Harold C Haggncamp ATTO R N EY 1940- s. L. CLQTHIER EIAL 2,225,508

SCANNING METHOD AND APPARATUS Filed March 20, 1939 4 Sheets-Sheet 2 INVENTQRS Stem am L. Cloihz'er J BY Harold C. Hogezzcamp ATTORNEY Dec. 24, 19 0- s. L. CLOTHIER ETAL SCANNING METHOD AND APPARATUS Filed March 20, 1939 4 Sheets-Sheet 3 INVENTORS Siewari L. C'lofihiezf BY Harold C. Hogencam o 'f 'r'roRNEY Dec. 24, 1940.

s. L CLOTHI ER EIAL 2,226,508

SCANNING METHOD AND APPARATUS Filed March .20, 1939 4 Sheets-Sheet 4 INVENTORS Stewart L. Clozfhz'er & BY Harold CHogencamp gaggg mmm picture film and an illuminated animate object; and

Fig. 13 is an end view of a cathode ray tube illustrating the undulating scanning lines.

Fundamentally, the invention comprehends modifying the ordinary substantially straight elemental linear areas that are employed in analyzing a television image, by forming each linear area according to a unique predetermined pattern. These modified linear areas extend across the image in much the same fashion as heretofore with the exception that the composite elemental areas are not aligned in a straight path but rather they form an irregular line, typified by a broken curve, the contour of which curve followsa predetermined pattern. Various means may be employed to create the modified scanning line at the transmission apparatus, and to reproduce the same at the receiver. The principles of the invention have been set forth in our copending application Serial Number 104,172, filed October 6, 1936, of which this application forms a continuation-in-part. In the parent application the invention has been described in connection with television transmitters and receivers that employ mechanical scanning devices. As will be apparent from the following description, the invention is equally applicable to television systems employing electronic scanning devices, operating alone or in conjunction with mechanical scanning means.

The invention further comprehends illuminat- 7,

ing a. narrow transverse area of a strip of motion picture film in such a way that'the illuminated portion corresponds to an elemental linear area.

Accordingly the shape of the illuminated portion,

is optically defined by focussing thereon an image of an illuminated elongated aperture. Since thisv aperture is located at an appreciable distance from the film no dust particles are collected thereon from the film. It was formerly necessary to locate such plate as close as possible to the film to obtain a sharp image, but unless precautions were taken, the outline defined by the aperture became obscured by the gradual accumulation of dust and other foreign particles, either within the slot or in the zone between the slot and the film.

The advantages of the present invention will become apparent when it is realized that all ordinary television systems scan in a regular and orderly fashion, for example, by scanning the subject with successively adjoining straight lines. When the impulses from such television systems are broadcast by radio they may be received, and the images reconstructed, by any one in possession of standard receiving apparatus. The ready availability of broadcast television signals naturally operates to defeat the aims of any commercial television news agencies or photograph-transmitting enterprises that are obligated to restrict transmission to only duly authorized subscribers. By scanning along irregular paths in accordance with the teachings of the present invention, the signals when received by ordinary receiving equipment would result in the formation of images too distorted and unintelligible to be of value. A0 cording to the present invention only such per sons as are in possession of the key, or who are aware of the shape of the irregular linear area may properly receive the television signals. Unauthorized reception is further precluded by the inclusion of methods and apparatus for constantly or intermittently changing the shape of the elemental linear area at transmitter and receiver while the scanning system is in operation.

Since many of the various elements comprising the system are repeatedly illustrated throughout the several views to perform similar functions, identical reference numbers will be used, wherever convenient. to designate respectively similar parts.

In the arrangement shown in Fig. 1, a television transmitting apparatus embodying features of the invention comprises a source of high intensity illumination H such as an electric are or incandescent filament. A condensing lens l4 concentrates light rays emanating from the source I as a converging beam B upon a cylindrical converging lens H which further concentrates the light as a brilliantly luminous line across an aperture plate l5 having an elongated straight slot l9. A motion picture film |2 moves continuously past the slotted aperture plate l5 as by means of a set of rotating sprockets l3 in such a manner that the beam B passing through the slot I9, formed in the aperture plate l5, successively covers every portion of each film frame. Preferably the width of the slot I9 is equal to the width of the elemental linear area comprising a single line scan.

The beam B which accordingly passes through the film Has a fiat ribbon, also passes through a lens l8 and is then reflected from a scanner to form a series of successive linear images J corresponding to elemental linear areas. The linear images are scanned along their length into separate series of consecutively located elemental areas, which successively actuate a photoelectric cell 25. Any convenient form of scanner may be employed for this purpose, but we prefer to employ a rotatingdrum 2| driven at a constant speed as by means of a synchronous electric motor 22. The periphery of the drum 2| is provided with a series of scanning elements capable of forming a succession of images of the elemental linear areas. For purposes of illustrationthese scanning elements have been indicated in the drawings as a plurality of plane mirrors 23 which are fitted about the periphery of the drum 2|, all of which are identical in shape and size, and positioned at identical angles with respect to the axis of the drum 2|. The photocell 25 is spaced an appreciable distance from the periphery of the drum 2| and is provided with a slotted aperture plate 24 adjacent thereto upon which the projection lens IS, in conjunction with the mirrors 23, forms successive images J of the illuminated elemental linear area of the film l2, defined within the slot l9. Since the drum 2| is illustrated as rotating in a horizontal plane, and the slot I9 is horizontal, the images J move horizontally across the plate 24 in end-to-end relation. The plate 24 is positioned with its longitudinal slot 2|] extending vertically so that as the images J pass the slot they are analyzed as a succession of elemental areas preferably of square configuration. The photocell 25 is arranged so that its active surface is exposed to substantially the entire length of the slotin the plate 24 so that any vertical shifting of the images J produced by vibration or other mechanical error in the scanning drum 2| produced no ill effect in the analysis of the images J, but merely raises or lowers them along the slot 20. This procedure eliminates distortion which would otherwise be'present if the aperture plate 24 were provided with an opening of square configuratiomas it is extremely diflicult to maintain the images J in constant alignment with such a small opening. The photocell terminals it connect with an amplifier of As pointed out, the slot IS in the plate l corresponds in size and shape with an elemental linear area of the film l2. The width or height of the slot I9 is determined by the number of line scans desired, and the size of each film frame. For example, with standard film having a frame height of three-fourths inch, the slot i9 preferably has a width of 0.0025 inch when 300 lines or elemental linear areas per frame are desired. The width of the slot 20 in the plate 24 is determined principally by the width of the images J and by the desired shape of the elemental areas. Assuming that the dimensions of the images J formed on the plate 24 by the lens l8 are increased six fold over the dimensions of the slot l9 and, that elemental areas of square shape are desired, the slot 20 should have a width of 0.015 inch. If the elemental areas are to be of other rectangular shape, the width of the slot 20 may be correspondingly varied.

The television transmitting apparatus shown in Fig. 2 is very similar to that shown in Fig. 1 with the exception that the positions of the aperture plate l5 and the lenses have been substantially interchanged. With this arrangement, light from the source II is concentrated directly upon the plate l5 as by means of the cylindrical lens H. A narrow band of light for illuminating an elemental linear area is focussed as an image of the aperture l5 upon the film l2 by means of the lens I4. As the film I2 is moved longitudinally by sprockets l3, images J of successive illuminated bands on the film are formed upon the surface of the plate 24 by the lens I8 and mirrors 23, which images excite the photocell 25 after passing through the slot 20 in the plate 24. By this arrangement a clearly defined linear area is optically formed on the film 12, which area remains sharply illuminated during operation, unaffected by dust particles that otherwise tend to collect within the slot IQ of the aperture plate liwhen it is positioned closely adjacent to the film as shown in Fig. 1. Furthermore, the linear area remains free of shadowy and indistinct outlines, such as are likely to be formed when the plate I5 is positioned adjacent to the film as shown in Fig. 1, though spaced substantially from the film to minimize the collection of dust and other foreign particles.

Signals transmitted by the apparatus shown in Figs. 1 and 2 may be received and transformed into visual images by a receiver of conventional design as the scanning is performed along consecutively positioned straight lines, in accord with standard practice. In order to restrict reception to authorized persons, or in effect to transmit signals secretly it has been found necessary only to change the shapeof the straight elemental linear area to one of irregular configuration. This may be accomplished through the use of a modified aperture plate l5, shown in Figs. 3 and 4. The aperture plate i5 comprises essentially a mask of thin sheet material provided with an irregular slot, by which is meant a slot having a shape other than straight. For example. the slot may have the configuration of an undulating curve, such as a sinusoidal wave, though preferably it consists of a broken curve, formed for example, of a series of short, connected, straight lines disposed to form a sawtooth shape or a configuration resembling the edge of a key designed for a tumbler lock.

Otherwise the shape of the slot may represent a combination of two or more of the foregoing shapes, the purpose being to form an elongated irregular opening which is diflicult to reproduce. The aperture plate i5 shown in Figs. 3 and 4 preferably comprises a frame 21 to which is secured a pair of laminae or sheets 26 and 29, assembled in coplanar juxtaposed relation with adjacent bevelled edges 23 and 3| respectively defining an irregular slot 32 of substantially uniform width. The sheets may be mounted to the frame 21 in any convenient manner as by screws 34 which may project through elongated apertures 33 in at least one of the sheets 26 or 29 so that the width of the slot 32 may be adjusted. The sheets forming the laminae 2.6 and 29 may consist of any desired opaque material, for example, paper, cardboard or sheet metal. In the event that thin metal foil or the like is employed, use may be'made of a transparent backing material such as glass, Celluloid, etc., for additional support.

The aperture plate l5 may be substituted in either of the transmitting systems indicated in Figs. 1 or 2 to replace the aperture plate i5 having a straight slot IS with the exception that the beam cannot then be concentrated to a fine straight line at the mask but must be of such cross section as to fully illuminate the aperture opening. In either case the beam B after passing through the plate is in the form of a ribbon, the cross-section of which corresponds with the shape of the slot in the plate. Images formed on the aperture plate 24 do not consist of single straight lines but rather irregularlines simulating the shape of the slot 32. Each of the images reflected by the mirrors 23 successively passes longitudinally in a direction transversely of the slot 20 in the plate 24. When an aperture plate of the type shown in Fig. 3 is employed, the slot 20 must be long enough to accommodate the lateral displacement of the irregular linear images so that they are at no' time screened from the photocell 25.

In order to more fully insure secrecy of the transmitted signals and to more completely guarantee their reception by only authorized persons,

use may be made of an aperture plate or mask l5" having a slot of continuously varying configuration as shown in Fig. 5. In order toaccomplish this result the plate l5 may be provided with a slot 32 of relatively greatlengthwhich may be oscillated slowly or otherwise moved in a predetermined manner with respect to the film l2 or other object being scanned. Preferably, however, the mask l5" comprises an opaque belt 36 provided with a translucent or transparent linear area of irregular configuration 32'. The belt 30 may be composed of Celluloid or gelatin, the surface of which is rendered substantially opaque on opposite sides of the area 32 by photographic or other means. The irregular linear area 32', which is sufiiciently clear to permit the passage of light, corresponds to the slot 32 in the aperture plate IS. The belt 30 may be made to move longitudinally either continuously or intermittently at a relatively slow rate of speed be employed at the receiving station, and must be moved in synchronism with the mask at the transmitting station. Obviously, the rate of motion of the mask must be sufficiently slow that it does not produce apparent distortion.

In Fig. 6 is disclosed apparatus for transmitting television signals according to the present ror 38 is preferably a, first-surface plane reflector pivoted at or near its midsection substantially in the plane of the reflecting surface. A lever arm 4|, secured to the mirror 38, extends away from the pivotal mounting, being provided with a follower 42 at the extremity of-the arm 4| for engagement with a rotatable cam 44 against whose surface the follower is continuously urged as by a spring 43. Rotation of the cam 44 causes the mirror 38 to oscillate through a small arc and to produce, in conjunction with the lens 36, a shifting image of the object 0, preferably in the plane of the plate l5.

Means is provided to divide or analyze the image thus formed into a series of elemental linear areas preferably of irregular configuration. Such means may comprise an aperture plate IE or mask l5" of the type disclosed in Figs. 3 or 5. The plate l5 shown in Fig. 6 is positioned substantially in the plane of the image of the object formed by the lens 36 and the mirror 38, and is arranged so that the slot 32, representing an elemental linear area, extends longitudinally in a direction generally parallel with the axis of the mirror 38. The beam B passing through the aperture plate I5 is projected through a lens 45 upon the mirrored periphery of a scanning drum or other similar means 2|. Separate images J of the slot 32, designating elemental linear areas, are formed at a distance from the periphery upon an aperture plate 24. The plate 24 is positioned adjacent to a photocell 25 with the slot 20 extending substantially at right angles to the images J. As the drum 2| rotates, the images J. produced by reflection from the respective scanning elements 23 on the drum 2|, pass successively in end-to-end relation transversely across the slot 20 and separately excite the photocell 25, the impulses from terminal wires l6 being amplified to form the television signals.

Fig. 7 discloses a receiving apparatus, embodying features of our invention, which is capable of transforming back into visual images, television signals developed by transmitters of the type indicated in Figs. 1, 2 and 6. Identical reference characters are used to designate parts corresponding in function and design with those already described. Use is made of a source of high intensity illumination II, and a condensing lens 46 capable of directing rays from the light source II as a beam through a light modulating unit 41, of any conventional design, capable of acting upon the beam to vary its intensity in accordance with the electrical impulses received from the television transmitting station. The beam is concentrated upon an aperture plate 24 as by means of a cylindrical lens II. A scanning drum 2| provided with scanning elements 23 about its periphery and rotated by means of a motor 22 at a speed synchronized with a similar drum at the transmitting station is mounted in spaced relation to the plate 24. A lens 48, positioned between the plate 24 and the drum 2|, cooperates with the scanning elements 23 to form in the plane of the plate l5, a series of images J of the illuminated slot 20.

An aperture plate l5 having a slot 32 of a configuration identical with that employed in the transmitting apparatus is located so that the images J are formed upon or adjacent to its surface, the length of each image J being suflicient to accommodate the lateral displacement of the irregular slot 32. The slot 32 is so positioned with respect to the drum 2|, that the images are formed transversely on the slot 32 and move along the length of the slot. Successive portions of the slot 32 are accordingly illuminated by the movement of an image J along the slot, the intensity at any oint being dependent upon the brightness of the modulated image at the instant it passes such point. Images of the slot 32 are formed upon a screen S by means'ota projection lens 49 positioned between the platefli' and the rotating mirrored prism 39.

The speed of rotation of the prism 39 is synchronized with the transmission apparatus so as to form the desired number of frames per second, each surface forming a complete frame or field during a single vertical sweep, as from the top to the bottom of the screen. In the case of the transmitters shown in Figs. 1 and 2 the prism 39 is rotated at a speed synchronized with the speed of the sprockets l3 so that the same number of frames are formed per second. In the case of the transmitter shown in Fig. 6 the prism 39 is synchronized with the scanner 3! so that the same number of frames are formed per second. As the prism 39 rotates, successive adjacentlydisposed images of the illuminated irregular linear aperture 32 are formed upon the screen S to reconstruct the image of the. object scanned. Whenever a mask of the type shown in Fig. 5 is employed in the transmitting equipment, an identical mask is required in the receiving apparatus mounted in the position indicated by the plate I5 in Fig. '7, and synchronized so as to move at the same speed as the belt 30 in the transmitting equipment.

With slight modiflcation, the apparatus shown in Fig. 7 may be used as a direct pickup scanner for transmission, employing the flying spot method of scanning. For such use a constant intensity source of illumination is used and the light modulating unit 41 is omitted. The subject to be scanned is placed in the position occupied by the screen S of Fig. '7 and thus scanned by the moving spot of light. Light reflected from the subject is then used to activate photocells (not shown) according to the light and dark shaded elementary areas of the subject in the usual well known manner in which flying spot pickup is employed. In the present invention however the linear areas would of course follow the predetermined path deviating from a straight line according to the shape of the aperture employed in the plate l5.

Fig. 8 discloses a method by which the invention may be adapted for use in conjunction with an electron beam scanning apparatus, for examv ple a cathode ray tube. An aperture plate I5 of the type and design used at the transmitting v station is located directly adjacent to the screen end of a cathode ray tube C. Conventional horizontal deflection plates having external connections H, and vertical deflectionplates having external connections V are provided in order to de-- flect the electron beam in horizontal and vertical paths respectively. The intensity of the electron beam is controlled in a conventional manner by means of voltage applied to the control grid connection G by the received signal impulses. An electrical wave of relatively high frequency, and preferably inthe radio frequency range, is applied to the vertical deflection plates through connections V, the voltage'applied being sumcient to deflect the beam enough to accommodate the lateral deviation of the angularly related segments forming the slot 32 in the plate. l5. Saw tooth voltage is applied to the horizontal deflection plates through the connections H to provide horizontal sweep of the electron stream in synchronism with the line scanning, frequency. Accordingly as the respective voltages are applied to the connections G, H and V, and the tube is otherwise provided with the conventional operating potentials, the images of the successive scanning lines become visible through theslot 32, the respective portions representing varying degrees of luminosity in accordance with the intensity of the bombardment of the modulated electron stream on the portions of the fluorescent coating within the window 5| of the cathode ray tube C. The modulated irregular linear area visible thru the aperture slot of plate I5 is similar to that obtained on the plate l5 shown in Fig. 7, and the complete subject of transmission may then be reassembled as a visual image by the frame scan- I ning means 39 illustrated in Fig. '7, located between the aperture plate I5 and the screen S, and a projection lens 49 capable of forming an image of the modulated linear area upon the screen S. Ifdesired, means such as an oscillating scanner 31 of the type shown in Fig. 6 may be employed to sweep the irregular linear area vertically with respect to the screen S to form a complete image. The scanner 31, as previously described, comprises a plane reflecting mirror 38 oscillated by means of a cam 44 engaging an arm 4|, the cam being designed preferably to impart uniform angular motion to the mirror 38 throughout the scanning operation of the cycle followed by a quick return motion between frame scanning periods. A fixed plane mirror 52 is positioned for convenience in reflecting the beam from the scanner 31 upon the screen S, although it is to be understood that by proper orientation of the parts the images may be formed on the screen S without the use of mirror 52. The operation of the receiving apparatus shown in Fig. 8 is believed to be obvious from the foregoing description but may be described briefly as follows. The electron beam within the tube 0 is deflected horizontally and vertically to form a fluorescent light source behind the slot 32, the beam being modulated by the transmitted television signals. Sue cessive images of the slot 32 are formed upon the screen S by the lens 49 and scanner 31, each succeeding line image is placed adjacent to and directly beneath that of the previous line, the result being a complete image forming a copy of the subject of transmission.

In the arrangement shown in Fig. 8 only that portion of the luminous band on the window 5! which is visible thru the slot 32 is used in reproducing the subject of transmission. More eiflcient results may be obtained by eliminating the aperture plate l5 and reproducing the modulated linear area according to the predetermined pattern by suitable electromagnetic or electrostatic deflection of the electron beam within the tube 0. Accordingly, by applying a low voltage to the vertical deflection plates thru the connections V, and varying the voltage in accordance with the lateral displacement of the slot 32, while providing the usual horizontal deflection, the electron beam may be made to follow a course similar to the path designated by the slot 32. With such an arrangement'the necessary sweep voltage is applied to the horizontal deflection plates at line scanning frequency to sweep the beam generally along the length of the elemental linear area, and the varying low voltage is applied to the vertical deflection plates through the connection V to provide the desired degree of deviation of each linear area from a fixed norm.

The voltage applied to the connections V may be generated and controlled in various ways, for example, by periodically varying a resistance or potentiometer in accordance with the transverse deviation of the segments forming the irregular linear area, or by imposing the voltage wave of a signal generator upon the vertical deflection plates. For example, with a line deflection frequency of 2700 cycles applied to the terminals H, a line-distorting wave of 13,500 cycles may be applied to the connections V, the wave being of sinusoidal, saw-tooth or other predetermined shape as shown in Fig. 13. The frequency, amplitude, and/or shape of the line-distorting wave may be varied, either continuously or intermittently, according to a predetermined pattern, at a rate sufliciently slow as not to produce apparent distortion of the picture. Another form of apparatus which may be employed to generate the desired wave form is disclosed in Fig. 9. Use is made of a source of light I I, concentrated upon a straight elongated slot I9 formed in an aperture plate I5 as by means of a cylindrical converging lens ll. A projection lens I8 is adapted to form an image of the illuminated slot l9 in the plane of a mask 53 having an opening 54 the length of which corresponds with the overall length of an irregular linear area. The height of the opening varies along its length in accordance with the shape of the irregular slot 32, or in other words, in accordance with the degree of deviation from a flxed norm. As shown in Fig. 9 the mask 53 preferably comprises a frame having an elongated opening therein, one side of which is preferably straight, the other side being made of irregular contour to correspond with the contour of the desired irregular linear area. Successive images J of the slot I! are swept along the opening 54 as shown in Fig. 9 by means of a scanning drum 2| driven by a motor 22, the drum being provided about its periphery with mirror surfaces 23. A large condensing lens 55 concentrates the light which passes through the opening 54 upon a mits the passage to the photocell of a relatively large amount of light as a result of the relatively great length of image J exposed, thus producing a corresponding relatively high deflection voltage after proper amplification. The responses of the photocell are conducted through wires l6 to a suitableamplifier A of conventional design. said amplifier preferably being provided with a conventional gain control 55.. The amplified impulses leave the amplifier through wires 51, which wires may be attached. to the connections V in Fig. 8 to control the vertical deflection of the electron stream, so as to reproduce, in conjunction with the horizontal deflection and other tubecontrol elements, a modulated beam forming a. linear area on the window 5| which is similar in shape and illumination with acorresponding line at the transmitting apparatus. By this latter arrangement the irregular linear area represents a finite line of substantially constant thickness developed by the generation of an elemental area along a path, the direction of which deviates from a fixed norm, e. g., a straight line, by predetermined amounts during predetermined intervals of the line scanning period. If the voltage obtained from the connections 51 is superimposed upon the sweep voltage normally applied to the connections ,V to obtain frame scanning, a complete image of the subject of transmission is formed upon the window 5| of the cathode ray. tube 0, provided, of course, that the attending horizontal sweep voltage and modulating voltage are applied to the tube. In this manner the scanning mechanism 31 and the mask l5 may be dispensed with and the complete image may be viewed directly upon the window 5|, or the image may be focussed upon the screen S as by means of the lens 49. v

Fig. 10 discloses a cathode ray tube C provided with an opaque belt 30 of the type disclosed in Fig. 5. The belt 30 is moved longitudinally across the window 5| in predetermined fashion as by means of sprockets l3, the belt being substantially opaque with the exception of the irregular transparent linear area 32'. The belt 30 may be adapted for use with a system of the type disclosed in Fig. 8 wherein use is made of a linear,

area of continuously changing contour, both in the transmitter and receiver. Otherwise the mask 53 shown in Fig. 9 may be made to correspond'with the contour of the line 32' of the belt 30, in which case the mask 53 might also be made movable so as to obtain the vertical deflection voltages to be. applied to the connections V, to adapt the tube C for use with an irregular linear area of slowly changing configuration.

Fig. 11 discloses apparatus incorporating principles of the present invention for use with a conventional cathode ray transmitter tube. In this case the film apparatus is arranged in a manner similar to that disclosed in our copending patent application bearing Serial No. 195,938, filed March 15, 1938, except that a keyed aperture plate and electronic scanning is employed in this variation of the present invention. The apparatus disclosed in Fig. 11, which is specifically adapted for the television transmission of motion picture film, comprises a source of light II and a condensing lens I 4, adapted to illuminate a portion of a motion picture film I2.

fined within the slot 32 is formed upon the sensitive mosaic surface 59 of a cathode ray transmitting tube 58 by means of a converging lens 80. The respective elemental areas forming the irregular linear area focussed on the mosaic surface are successively scanned by means of sweep circuits operating substantially in the manner described in connection with the tube 0 of Fig. 8.

Fig. 12 illustrates a television transmitter incorporating electronic scanning wherein the subject of transmission comprises an animate object O or the like illuminated as by means of sources of illumination 35 as shown in Fig. 6. A converging lens 35 forms an image of the object 0 upon the sensitive mosaic surface 59 of a cathode ray transmitting tube 58. The horizontal and vertical deflection voltages applied to the tube 58 are conventional with the exception that the voltage across the wires 51 of the apparatus shown in Fig. 9 is superimposed upon the normal sweep voltage applied to the vertical deflection plates through connections V', thereby distorting the usual straight sweep of the electron scanning beam into one having the configuration of the desired irregular linear area. Obviously in any case where either the light beam or the electron beam is directed on the mosaic plate an oblique angle, proper keystone corrections are required.

It is obvious that various modifications will suggest themselves to those skilled in the art and that changes may be made in the apparatus and method herein disclosed without departing from the scope of the 'invention' or sacrificing any of its advantages. For example, while we have herein described our invention as applied to television, it is obvious that it is equally desirable and applicable in facsimile and film recording work.

We claim: I

1. In a television apparatus, in combination with means for scanning an object and analyzing an image of said object into a series of lines; an aperture plate adjacent to the image being scanned, said aperture'plate being provided with a slot of irregular configuration.

2. In a television apparatus as claimed in claim 1 including means for adjusting the width of the slot in said aperture plate.

3. In a television apparatus as claimed in claim 1 including means for moving the aperture plate with respect to the image being scanned, the rate of movement of said aperture plate being sufliciently slow as not to cause apparent distortion.

.4. In a television apparatus, in combination with means for scanning an image or object into a series of lines; aperture means comprising a substantially opaque belt provided with an irregular linear area capable of transmitting light, and means for moving said belt '30 as to form a linear aperture of continuously changing configuration with respect to the image being scanned, the rate of movement of said belt being suinciently slow as not to cause apparent distortion.

5. In a motion picture film scanning apparatus,

the combination with a beam of light for transmission through the film being scanned, and

means for moving the film longitudinally; of an aperture plate provided with an elongated slot of irregular configuration and positioned adjacent to and transversely of the film being scanned so as to intercept the beam of light, means for resolving the beam passing through the slot into a series of elemental areas, and a photoelectric c'ell positioned so as to have superimposed upon its active surface the successive elemental areas.

6. A television system inclusive 0! object scanning and analyzing means having means casting an irregular concentrated line of light, and means dividing said line into a number of elemental areas.

7. In television scanning apparatus, the combination which includes an aperture member provided with a slot of patterned irregular linear configuration and uniform thickness, and means producing an image of the slot for analyzing the subject scanned into linear areas of the pattern selected.

8. A television system inclusive of object scanning and analyzing means having means casting a varying irregular concentrated line of light,

and means analyzing said line into a, number of elemental areas.

9. In a method of scanning, the steps of analyzing an object for transmission along a series of scanning lines, each of which is identical and of predetermined irregular asymmetric pattern for the purpose of obtaining secrecy; and of recomposing the received image in like manner.

10. A scanning system including means for analyzing an image of an object for transmission along a series of scanning lines, each of which is identical and of predetermined irregular asymmetric configuration for the purpose of obtaining secrecy; and means for recomposing the image in like manner for viewing at a remote point.

STEWART L. CLOTHJER. HAROLD C. HOGENCAMP. 

